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  1. #1

    2010 VX Sport intake camshaft wear, bent exhaus valves, no compression in #2 & #4

    200 hour machine. Started to exhibit signs of loss of power (slower top end) in the last 50 hours or so. Put the ski up for 2 months, starting and running with out any issues. Went to start it (2 months later), to no avail. Was turning over slow. Thought is was a low batt. Not the case. Have no compression is #2 and #4 cylinders. (110 in 1 and 3 and ZERO in 2 and 4). Tore engine apart. Here is the strange part: 2 injectors are bad (letting air through). 2 exhaust valves bent. Middle lobes on ALL of the intake (cam) are completely wiped out. Not rough, just wiped out.
    My best guess: Injectors pumped fuel into the cylinders, hydrolocked #2 and #4, bending my valves.
    Camshft issue (completely separate). Either bad cam from the factory or an oil pump issue. However, the top end had plenty of oil and everything else looks 100%.
    I thought I knew these engines fairly well. Have 6 skis. But this one is a mystery.
    I can put in new valves, injectors and cam, but would like to know what can possibly cause this type(s) of failure at 200 hours. I've had machines (Yamahas) with 600 hours and no wear.
    They are used in salt water, but get flushed after every use and sit on a dry dock.
    Any help would be appreciated.

  2. #2
    Update: Cam must have been a bad run from Yamaha. No other explanation. Everything else in the top end is 100%. My best guess is that the valves hung up from sitting for 2 months. Piston smacked them back into place and bent 2 exhaust valves. Have parts on order. Even more perplexing:
    I swapped out a motor out of an 05 (which ran well just before the swap). Now the damn thing will not start. Checked every flipping thing (even the timing). I have YDS and everythign is within spec. I even swapped the power pack, the TPS and ECM. Nothing. Have excellent spark, good compression and plugs are getting fuel. I cycled the injectors, fuel pump, coils, etc... Does anyone know if the timing is different from 2005 to 2011 (ie: have to change the deg. of BTDC for the 2011 electronics to work). I would never imagine that Yamaha would do something like that, but I'm running out of ideas.

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